A line or straight passage, or the position of that which lies in a straight line.

2015 January 4, Harry Mount, “Kings and queens – any other approach to history is boring [print version: Game of thrones, 3 January 2015, p. R22]”, in The Daily Telegraph (Review)[1]:

In his Booker Prize-winning novel The Line of Beauty, Alan Hollinghurst wrote about people who know their world history as being able to look back through the millennia as an enfilade of rooms: Greece yields to Rome; Rome to the Byzantine Empire ... the Renaissance ... the British Empire ... America ... China. The same goes for people who can recite their kings and queens. British history clicks into a long enfilade of discrete, identifiable periods.